update safety client app to use new register flow

[dineshyv]

This can only land after the sdk has been updated
Testing:

PYTHONPATH=. python -m examples.safety.client localhost 5000 <bedrockprovideid>
{
    "identifier": "shield_id",
    "params": {
        "guardrailVersion": "DRAFT"
    },
    "provider_id": "remote::bedrock",
    "provider_resource_id": "<bedrockprovideid>",
    "shield_type": "generic_content_shield",
    "type": "shield"
}
RunShieldResponse(violation=SafetyViolation(metadata={'contentPolicy': {'filters': [{'type': 'VIOLENCE', 'confidence': 'LOW', 'filterStrength': 'HIGH', 'action': 'BLOCKED'}]}, 'invocationMetrics': {'guardrailProcessingLatency': 346, 'usage': {'topicPolicyUnits': 0, 'contentPolicyUnits': 1, 'wordPolicyUnits': 0, 'sensitiveInformationPolicyUnits': 0, 'sensitiveInformationPolicyFreeUnits': 0, 'contextualGroundingPolicyUnits': 0}, 'guardrailCoverage': {'textCharacters': {'guarded': 93, 'total': 93}}}}, violation_level='error', user_message='Sorry, the model cannot answer this question.'))